Video-Based Point Cloud Compression (V-PCC) Component Synchronization

ABSTRACT

A method is implemented by a PCC decoder and comprises: receiving, by the PCC decoder, a point cloud bitstream; performing, by the PCC decoder, buffering of the point cloud bitstream based on a time, the performing comprising determining the time based on a delay and a delay offset; and decoding, by the PCC decoder, the point cloud bitstream based on the buffering. A method is implemented by a PCC decoder and comprises: receiving, by the PCC decoder, a point cloud bitstream; performing, by the PCC decoder, buffering of the point cloud bitstream based on a delay, the delay is based on a first delay and a second delay; and decoding, by the PCC decoder, the point cloud bitstream based on the buffering.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of Int'l Patent App. No. PCT/US2020/054414 filedon Oct. 6, 2020, which claims priority to U.S. Prov. Patent App. No.62/911,813 filed on Oct. 7, 2019, both of which are incorporated byreference.

TECHNICAL FIELD

The disclosed embodiments relate to PCC in general and V-PCC componentsynchronization in particular.

BACKGROUND

The amount of video data needed to depict even a relatively short videocan be substantial, which may result in difficulties when the data is tobe streamed or otherwise communicated across a communications networkwith limited bandwidth capacity. Thus, video data is generallycompressed before being communicated across modern daytelecommunications networks. The size of a video could also be an issuewhen the video is stored on a storage device because memory resourcesmay be limited. Video compression devices often use software and/orhardware at the source to code the video data prior to transmission orstorage, thereby decreasing the quantity of data needed to representdigital video images. The compressed data is then received at thedestination by a video decompression device that decodes the video data.With limited network resources and ever increasing demands of highervideo quality, improved compression and decompression techniques thatimprove compression ratio with little to no sacrifice in image qualityare desirable.

SUMMARY

A first aspect relates to a method implemented by a PCC decoder andcomprising:

-   -   receiving, by the PCC decoder, a point cloud bitstream;        performing, by the PCC decoder, buffering of the point cloud        bitstream based on a time, the performing comprising determining        the time based on a delay and a delay offset; and decoding, by        the PCC decoder, the point cloud bitstream based on the        buffering.

The embodiments provide for a schema in which decoded V-PCC componentsare output at a corresponding component decoder, referred to as CP A,and are transferred to the buffer, where the synchronization process isimplemented in order to prepare the data to for reconstruction at CP B.An output delay synchronization is used in the synchronization process.The output delay synchronization improves synchronization, which reducesthe buffer memory size.

Optionally, in any of the preceding aspects, the time is further basedon a removal time.

Optionally, in any of the preceding aspects, the time is further basedon ClockTick.

Optionally, in any of the preceding aspects, the time is further basedon a first expression of the delay and the delay offset.

Optionally, in any of the preceding aspects, the time is further basedon a second expression, and the second expression is a product ofClockTick and the first expression.

Optionally, in any of the preceding aspects, the time is further basedon a sum of the removal time and the second expression.

Optionally, in any of the preceding aspects, the point cloud bitstreamcomprises a plurality of components.

Optionally, in any of the preceding aspects, the components comprise anoccupancy map.

Optionally, in any of the preceding aspects, the components comprisegeometry data.

Optionally, in any of the preceding aspects, the components compriseattribute data.

Optionally, in any of the preceding aspects, the components comprise anatlas frame.

Optionally, in any of the preceding aspects, the time is further basedon a number of the components.

Optionally, in any of the preceding aspects, the time isDpbDabOutputTime.

Optionally, in any of the preceding aspects, the delay isPicAtlasDpbOutputDelay.

Optionally, in any of the preceding aspects, the delay offset isDpbDabDelayOffset.

Optionally, in any of the preceding aspects, DpbDabDelayOffset is equalto a difference between MaxlnitialDelay and PicAtlasDpbOutputDelay.

Optionally, in any of the preceding aspects, the method furthercomprises: storing the point cloud bitstream; and displaying a pictureor a video from the point cloud bitstream.

A second aspect relates to a method implemented by a PCC decoder andcomprising:

-   -   receiving, by the PCC decoder, a point cloud bitstream;        performing, by the PCC decoder, buffering of the point cloud        bitstream based on a delay, the delay is based on a first delay        and a second delay; and decoding, by the PCC decoder, the point        cloud bitstream based on the buffering.

Optionally, in any of the preceding aspects, the delay is further basedon a maximum of the first delay and the second delay.

Optionally, in any of the preceding aspects, the delay isMaxlnitialDelay.

Optionally, in any of the preceding aspects, the first delay isMaxlnitDelay.

Optionally, in any of the preceding aspects, the second delay isPicAtlasDpbOutputDelay.

Optionally, in any of the preceding aspects, the buffering is furtherbased on DpbDabDelayOffset, and whereinDpbDabDelayOffset=MaxlnitialDelay−PicAtlasDpbOutputDelay.

Optionally, in any of the preceding aspects, the method furthercomprises: storing the point cloud bitstream; and displaying a pictureor a video from the point cloud bitstream.

Any of the above embodiments may be combined with any of the other aboveembodiments to create a new embodiment. These and other features will bemore clearly understood from the following detailed description taken inconjunction with the accompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 is a flowchart of an example method of coding a video signal.

FIG. 2 is a schematic diagram of an example coding and decoding (codec)system for video coding.

FIG. 3 is a schematic diagram illustrating an example video encoder.

FIG. 4 is a schematic diagram illustrating an example video decoder.

FIG. 5 is an example of point cloud media that can be coded according toPCC mechanisms.

FIG. 6 is an example of patches created from a point cloud.

FIG. 7A illustrates an example occupancy frame associated with a set ofpatches.

FIG. 7B illustrates an example geometry frame associated with a set ofpatches.

FIG. 7C illustrates an example atlas frame associated with a set ofpatches.

FIG. 8 is a schematic diagram of an example conformance testingmechanism.

FIG. 9 is a schematic diagram of an example HRD configured to perform aconformance test on a PCC bitstream.

FIG. 10 is a schematic diagram illustrating an example PCC bitstream.

FIG. 11 is a schematic diagram of an example video coding device.

FIG. 12 is a schematic diagram of component synchronization in pointcloud reconstruction.

FIG. 13 is a schematic diagram demonstrating a maximum delay calculationfor a single map.

FIG. 14 is a schematic diagram demonstrating a maximum delay calculationfor multiple maps.

FIG. 15 is a flowchart illustrating a method of decoding a bitstreamaccording to a first embodiment.

FIG. 16 is a flowchart illustrating a method of decoding a bitstreamaccording to a second embodiment.

DETAILED DESCRIPTION

It should be understood at the outset that, although an illustrativeimplementation of one or more embodiments are provided below, thedisclosed systems and/or methods may be implemented using any number oftechniques, whether currently known or in existence. The disclosureshould in no way be limited to the illustrative implementations,drawings, and techniques illustrated below, including the exemplarydesigns and implementations illustrated and described herein, but may bemodified within the scope of the appended claims along with their fullscope of equivalents.

The following abbreviations apply:

-   -   ASIC: application-specific integrated circuit    -   AU: access unit    -   BT: binary tree    -   CAB: coded atlas buffer    -   CABAC: context-adaptive binary arithmetic coding    -   CAVLC: context-adaptive variable-length coding    -   Cb: blue difference chroma    -   CP A: conformance point A    -   CP B: conformance point B    -   CPU: central processing unit    -   Cr: red difference chroma    -   CTB: coding tree block    -   CTU: coding tree unit    -   CU: coding unit    -   DAB: decoded atlas buffer    -   DC: direct current    -   DCT: discrete cosine transform    -   DMM: depth modeling mode    -   DPB: decoded picture buffer    -   DSP: digital signal processor    -   DST: discrete sine transform    -   EO: electrical-to-optical    -   FIFO: first-in, first-out    -   FPGA: field-programmable gate array    -   HEVC: High Efficiency Video Coding    -   HRD: hypothetical reference decoder    -   HSS: hypothetical stream scheduler    -   ID: identifier    -   I/O: input/output    -   NAL: network abstraction layer    -   OE: optical-to-electrical    -   PCC: point cloud compression    -   PIPE: probability interval partitioning entropy    -   PU: prediction unit    -   QT: quad tree    -   RAM: random-access memory    -   RDO: rate-distortion optimization    -   RGB: red, green, and blue    -   ROM: read-only memory    -   SAD: sum of absolute differences    -   SAO: sample adaptive offset    -   SBAC: syntax-based arithmetic coding    -   SEI: supplemental enhancement information    -   SPS: sequence parameter set    -   SRAM: static random-access memory    -   SSD: sum of squared differences    -   TCAM: ternary content-addressable memory    -   TT: triple tree    -   TU: transform unit    -   TX/RX: transceiver unit    -   V-PCC: video-based PCC    -   2D: two-dimensional    -   3D: three-dimensional.

The following terms are defined as follows unless otherwise specified.Terms may be described differently in different contexts. Accordingly,the following definitions should be considered as a supplement andshould not be considered to limit any other definitions of descriptionsprovided.

An encoder is a device that is configured to employ encoding processesto compress point cloud data into a bitstream. A decoder is a devicethat is configured to employ decoding processes to reconstruct pointcloud data from a bitstream for display. A point cloud/point cloudrepresentation is a group of points (e.g., samples) in 3D space, whereeach point may contain a position and optionally an attribute such ascolor. A bitstream is a sequence of bits, including point cloud data,that is compressed for transmission between an encoder and a decoder. Ina PCC context, a bitstream includes a sequence of bits of coded V-PCCcomponents.

A V-PCC component, or more generally a PCC component, may be atlas data,occupancy map data, geometry data, or attribute data of a particulartype that is associated with a V-PCC point cloud. An atlas may be acollection of 2D bounding boxes, or patches, projected into rectangularframes that correspond to a 3D bounding box in 3D space, where each 2Dbounding box represents a subset of a point cloud. An occupancy map maybe a 2D array corresponding to an atlas whose values indicate, for eachsample position in the atlas, whether that position corresponds to avalid 3D point in the point cloud representation. A geometry map may bea 2D array created through the aggregation of the geometry informationassociated with each patch, where geometry information may be a set ofCartesian coordinates associated with a point cloud frame. An attributemay be a scalar or vector property optionally associated with each pointin a point cloud and may refer to color, reflectance, surface normal,time stamps, or a material ID. A complete set of atlas data, occupancymaps, geometry maps, or attributes associated with a particular timeinstance may be referred to as an atlas frame, an occupancy map frame, ageometry frame, and an attribute frame, respectively. Atlas data,occupancy map data, geometry data, or attribute data may be componentsof a point cloud, and hence may be referred to as atlas components,occupancy map components, geometry components, and attribute framecomponents, respectively.

An AU may be a set of NAL units that are associated with each otheraccording to a specified classification rule and pertain to oneparticular output time. A coded component may be data that has beencompressed for inclusion in a bitstream. A decompressed component may bedata from a bitstream or sub-bitstream that has been reconstructed aspart of a decoding process or as part of an HRD conformance test. A HRDmay be a decoder model operating on an encoder that checks thevariability of bitstreams produced by an encoding process to verifyconformance with specified constraints. An HRD conformance test maydetermine whether an encoded bitstream complies with a standard. Aconformance point may be a point in a decoding/reconstruction processwhere an HRD performs an HRD conformance check to verify thatdecompressed or reconstructed data comply with a standard. HRDparameters may be syntax elements that initialize or define operationalconditions of an HRD. An SEI message may be a syntax structure withspecified semantics that conveys information that is not needed bydecoding processes in order to determine the values of samples indecoded pictures. A buffering period SEI message may be an SEI messagethat contains data indicating initial removal delays related to a CAB inan HRD. An atlas frame timing SEI message may contain data indicating aremoval delay relating to a CAB and an output delay related to a DAB ina HRD. A reconstructed point cloud may be a point cloud that isgenerated based on data from the PCC bitstream. A reconstructed pointcloud should approximate the point cloud that is coded into the PCCbitstream.

A decoding unit may be any coded component from a bitstream orsub-bitstream that is stored in a buffer for decoding. A CAB removaldelay may be an amount of time a component can remain in the CAB priorto removal. An initial CAB removal delay may be an amount of time acomponent in a first AU in a bitstream or sub-bitstream can remain inthe CAB prior to removal. A DAB may be a FIFO buffer in an HRD thatcontains decoded atlas frames in decoding order for use during PCCbitstream conformance testing. A DAB output delay may be an amount oftime a decoded component can remain in the DAB prior to being output(e.g., as part of a reconstructed point cloud).

V-PCC is a mechanism for efficiently coding 3D objects represented by acloud of points of varying attributes. Specifically, V-PCC is employedto encode or decode such point clouds for display as part of a videosequence. The point cloud is captured over time and included in PCCframes. The PCC frames are split into PCC components, which are thenencoded. The position of each valid point in the cloud at a timeinstance is stored as a geometry map in a geometry frame. The colors arestored as an attribute frame. Specifically, the patches at an instant intime are packed into an atlas frame. The patches generally do not coverthe entire atlas frame. Accordingly, occupancy frames are also generatedand indicate which portions of atlas frames contain valid patch data.Optionally, attributes of the points, such as transparency, opacity,and/or other data, may be included in an attribute frame. As such, eachPCC frame can be encoded as a plurality of frames containing differentcomponents describing the point cloud at a corresponding instant.Further, different components may be coded by employing different codingand decoding systems.

FIG. 1 is a flowchart of an example operating method 100 of coding avideo signal. Specifically, a video signal is encoded at an encoder. Theencoding process compresses the video signal by employing variousmechanisms to reduce the video file size. A smaller file size allows thecompressed video file to be transmitted toward a user, while reducingassociated bandwidth overhead. The decoder then decodes the compressedvideo file to reconstruct the original video signal for display to anend user. The decoding process generally mirrors the encoding process toallow the decoder to consistently reconstruct the video signal.

At step 101, the video signal is input into the encoder. For example,the video signal may be an uncompressed video file stored in memory. Asanother example, the video file may be captured by a video capturedevice, such as a video camera, and encoded to support live streaming ofthe video. The video file may include both an audio component and avideo component. The video component contains a series of image framesthat, when viewed in a sequence, gives the visual impression of motion.The frames contain luma components, or luma samples, which are pixelsexpressed in terms of light, and contain chroma components, or chromasamples, which are pixels expressed in terms of color. In some examples,the frames may also contain depth values to support 3D viewing.

At step 103, the video is partitioned into blocks. Partitioning includessubdividing the pixels in each frame into square or rectangular blocksfor compression. For example, in HEVC, the frame can first be dividedinto CTUs, which are blocks of a predefined size (e.g., 64×64 pixels).The CTUs contain both luma and chroma samples. Coding trees may beemployed to divide the CTUs into blocks and then recursively subdividethe blocks until configurations are achieved that support furtherencoding. For example, luma components of a frame may be subdivideduntil the individual blocks contain relatively homogenous lightingvalues. Further, chroma components of a frame may be subdivided untilthe individual blocks contain relatively homogenous color values.Accordingly, partitioning mechanisms vary depending on the content ofthe video frames.

At step 105, various compression mechanisms are employed to compress theimage blocks partitioned at step 103. For example, inter-prediction orintra-prediction may be employed. Inter-prediction takes advantage ofthe fact that objects in a common scene tend to appear in successiveframes. Accordingly, a block depicting an object in a reference frameneed not be repeatedly described in adjacent frames. Specifically, anobject such as a table may remain in a constant position over multipleframes. Hence the table is described once, and adjacent frames can referback to the reference frame. Pattern matching mechanisms may be employedto match objects over multiple frames. Further, moving objects may berepresented across multiple frames, for example, due to object movementor camera movement. As a particular example, a video may show anautomobile that moves across the screen over multiple frames. Motionvectors can be employed to describe such movement. A motion vector is a2D vector that provides an offset from the coordinates of an object in aframe to the coordinates of the object in a reference frame. As such,inter-prediction can encode an image block in a current frame as a setof motion vectors indicating an offset from a corresponding block in areference frame.

Intra-prediction encodes blocks in a common frame. Intra-predictiontakes advantage of the fact that luma and chroma components tend tocluster in a frame. For example, a patch of green in a portion of a treetends to be positioned adjacent to similar patches of green.Intra-prediction employs multiple directional prediction modes (e.g., 33in HEVC), a planar mode, and a DC mode. The directional modes indicatethat a current block is similar to or the same as samples of a neighborblock in a corresponding direction. Planar mode indicates that a seriesof blocks along a row/column (e.g., a plane) can be interpolated basedon neighbor blocks at the edges of the row. Planar mode, in effect,indicates a smooth transition of light/color across a row/column byemploying a relatively constant slope in changing values. DC mode isemployed for boundary smoothing and indicates that a block is similar toor the same as an average value associated with samples of all theneighbor blocks associated with the angular directions of thedirectional prediction modes. Accordingly, intra-prediction blocks canrepresent image blocks as various relational prediction mode valuesinstead of the actual values. Further, inter-prediction blocks canrepresent image blocks as motion vector values instead of the actualvalues. In either case, the prediction blocks may not exactly representthe image blocks in some cases. Any differences are stored in residualblocks. Transforms may be applied to the residual blocks to furthercompress the file.

At step 107, various filtering techniques may be applied. In HEVC, thefilters are applied according to an in-loop filtering scheme. Theblock-based prediction discussed above may result in the creation ofblocky images at the decoder. Further, the block-based prediction schememay encode a block and then reconstruct the encoded block for later useas a reference block. The in-loop filtering scheme iteratively appliesnoise suppression filters, de-blocking filters, adaptive loop filters,and SAO filters to the blocks/frames. These filters mitigate suchblocking artifacts so that the encoded file can be accuratelyreconstructed. Further, these filters mitigate artifacts in thereconstructed reference blocks so that artifacts are less likely tocreate additional artifacts in subsequent blocks that are encoded basedon the reconstructed reference blocks.

Once the video signal has been partitioned, compressed, and filtered,the resulting data is encoded in a bitstream at step 109. The bitstreamincludes the data discussed above, as well as any signaling data desiredto support proper video signal reconstruction at the decoder. Forexample, such data may include partition data, prediction data, residualblocks, and various flags providing coding instructions to the decoder.The bitstream may be stored in memory for transmission toward a decoderupon request. The bitstream may also be broadcast or multicast toward aplurality of decoders. The creation of the bitstream is an iterativeprocess. Accordingly, steps 101, 103, 105, 107, and 109 may occurcontinuously or simultaneously over many frames and blocks. The stepsshown in FIG. 1 may be in another suitable order.

The decoder receives the bitstream and begins the decoding process atstep 111. Specifically, the decoder employs an entropy decoding schemeto convert the bitstream into corresponding syntax and video data. Thedecoder employs the syntax data from the bitstream to determine thepartitions for the frames at step 111. The partitioning should match theresults of block partitioning at step 103. Entropy encoding/decoding asemployed in step 111 is now described. The encoder makes many choicesduring the compression process, such as selecting block partitioningschemes from several possible choices based on the spatial positioningof values in the input images. Signaling the exact choices may employ alarge number of bins. A bin is a binary value that is treated as avariable (e.g., a bit value that may vary depending on context). Entropycoding allows the encoder to discard any options that are clearly notviable for a particular case, leaving a set of allowable options. Eachallowable option is then assigned a code word. The length of the codeword is based on the number of allowable options (i.e., one bin for twooptions, two bins for three to four options, etc.) The encoder thenencodes the code word for the selected option. This scheme reduces thesize of the code words as the code words are as big as desired touniquely indicate a selection from a small subset of allowable optionsas opposed to uniquely indicating the selection from a potentially largeset of all possible options. The decoder then decodes the selection bydetermining the set of allowable options in a similar manner to theencoder. By determining the set of allowable options, the decoder canread the code word and determine the selection made by the encoder.

At step 113, the decoder performs block decoding. Specifically, thedecoder employs reverse transforms to generate residual blocks. Then thedecoder employs the residual blocks and corresponding prediction blocksto reconstruct the image blocks according to the partitioning. Theprediction blocks may include both intra-prediction blocks andinter-prediction blocks as generated at the encoder at step 105. Thereconstructed image blocks are then positioned into frames of areconstructed video signal according to the partitioning data determinedat step 111. Syntax for step 113 may also be signaled in the bitstreamvia entropy coding as discussed above.

At step 115, filtering is performed on the frames of the reconstructedvideo signal in a manner similar to step 107 at the encoder. Forexample, noise suppression filters, de-blocking filters, adaptive loopfilters, and SAO filters may be applied to the frames to remove blockingartifacts. Once the frames are filtered, the video signal can be outputto a display at step 117 for viewing by an end user.

FIG. 2 is a schematic diagram of an example coding and decoding (codec)system 200 for video coding. Specifically, codec system 200 providesfunctionality to support the implementation of operating method 100.Codec system 200 is generalized to depict components employed in both anencoder and a decoder. Codec system 200 receives and partitions a videosignal as discussed with respect to steps 101 and 103 in operatingmethod 100, which results in a partitioned video signal 201. Codecsystem 200 then compresses the partitioned video signal 201 into a codedbitstream when acting as an encoder as discussed with respect to steps105, 107, and 109 in method 100. When acting as a decoder, codec system200 generates an output video signal from the bitstream as discussedwith respect to steps 111, 113, 115, and 117 in operating method 100.The codec system 200 includes a general coder control component 211, atransform scaling and quantization component 213, an intra-pictureestimation component 215, an intra-picture prediction component 217, amotion compensation component 219, a motion estimation component 221, ascaling and inverse transform component 229, a filter control analysiscomponent 227, an in-loop filters component 225, a decoded picturebuffer component 223, and a header formatting and CABAC component 231.Black lines indicate movement of data to be coded, and dashed linesindicate movement of control data that control the operation of othercomponents. The components of codec system 200 may all be present in theencoder. The decoder may include a subset of the components of codecsystem 200. For example, the decoder may include the intra-pictureprediction component 217, the motion compensation component 219, thescaling and inverse transform component 229, the in-loop filterscomponent 225, and the decoded picture buffer component 223.

The partitioned video signal 201 is a captured video sequence that hasbeen partitioned into blocks of pixels by a coding tree. A coding treeemploys various split modes to subdivide a block of pixels into smallerblocks of pixels. These blocks can then be further subdivided intosmaller blocks. The blocks may be referred to as nodes on the codingtree. Larger parent nodes are split into smaller child nodes. The numberof times a node is subdivided is referred to as the depth of thenode/coding tree. The divided blocks can be included in CUs. Forexample, a CU can be a sub-portion of a CTU that contains a luma block,Cr blocks, and Cb block, along with corresponding syntax instructionsfor the CU. The split modes may include a BT, TT, and QT employed topartition a node into two, three, or four child nodes, respectively, ofvarying shapes depending on the split modes employed. The partitionedvideo signal 201 is forwarded to the general coder control component211, the transform scaling and quantization component 213, theintra-picture estimation component 215, the filter control analysiscomponent 227, and the motion estimation component 221 for compression.

The general coder control component 211 is configured to make decisionsrelated to coding of the images of the video sequence into the bitstreamaccording to application constraints. For example, the general codercontrol component 211 manages optimization of bitrate/bitstream sizeversus reconstruction quality. Such decisions may be made based onstorage space/bandwidth availability and image resolution requests. Thegeneral coder control component 211 also manages buffer utilization inlight of transmission speed to mitigate buffer underrun and overrunissues. To manage these issues, the general coder control component 211manages partitioning, prediction, and filtering by the other components.For example, the general coder control component 211 may dynamicallyincrease compression complexity to increase resolution and increasebandwidth usage or decrease compression complexity to decreaseresolution and bandwidth usage. Hence, the general coder controlcomponent 211 controls the other components of codec system 200 tobalance video signal reconstruction quality with bit rate concerns. Thegeneral coder control component 211 creates control data, which controlsthe operation of the other components. The control data is alsoforwarded to the header formatting and CABAC component 231 to be encodedin the bitstream to signal parameters for decoding at the decoder.

The partitioned video signal 201 is also sent to the motion estimationcomponent 221 and the motion compensation component 219 forinter-prediction. A frame or slice of the partitioned video signal 201may be divided into multiple video blocks. Motion estimation component221 and the motion compensation component 219 perform inter-predictivecoding of the received video block relative to one or more blocks in oneor more reference frames to provide temporal prediction. Codec system200 may perform multiple coding passes, e.g., to select an appropriatecoding mode for each block of video data.

Motion estimation component 221 and motion compensation component 219may be highly integrated, but are illustrated separately for conceptualpurposes. Motion estimation, performed by motion estimation component221, is the process of generating motion vectors, which estimate motionfor video blocks. A motion vector, for example, may indicate thedisplacement of a coded object relative to a predictive block. Apredictive block is a block that is found to closely match the block tobe coded, in terms of pixel difference. A predictive block may also bereferred to as a reference block. Such pixel difference may bedetermined by SAD, SSD, or other difference metrics. HEVC employsseveral coded objects including a CTU, CTBs, and CUs. For example, a CTUcan be divided into CTBs, which can then be divided into CBs forinclusion in CUs. A CU can be encoded as a PU containing prediction dataor a TU containing transformed residual data for the CU. The motionestimation component 221 generates motion vectors, PUs, and TUs by usinga rate-distortion analysis as part of a rate distortion optimizationprocess. For example, the motion estimation component 221 may determinemultiple reference blocks, multiple motion vectors, etc. for a currentblock/frame, and may select the reference blocks, motion vectors, etc.having the best rate-distortion characteristics. The bestrate-distortion characteristics balance both quality of videoreconstruction (e.g., amount of data loss by compression) with codingefficiency (e.g., size of the final encoding).

In some examples, codec system 200 may calculate values for sub-integerpixel positions of reference pictures stored in decoded picture buffercomponent 223. For example, video codec system 200 may interpolatevalues of one-quarter pixel positions, one-eighth pixel positions, orother fractional pixel positions of the reference picture. Therefore,motion estimation component 221 may perform a motion search relative tothe full pixel positions and fractional pixel positions and output amotion vector with fractional pixel precision. The motion estimationcomponent 221 calculates a motion vector for a PU of a video block in aninter-coded slice by comparing the position of the PU to the position ofa predictive block of a reference picture. Motion estimation component221 outputs the calculated motion vector as motion data to headerformatting and CABAC component 231 for encoding and motion to the motioncompensation component 219.

Motion compensation, performed by motion compensation component 219, mayinvolve fetching or generating the predictive block based on the motionvector determined by motion estimation component 221. Again, motionestimation component 221 and motion compensation component 219 may befunctionally integrated, in some examples. Upon receiving the motionvector for the PU of the current video block, motion compensationcomponent 219 may locate the predictive block to which the motion vectorpoints. A residual video block is then formed by subtracting pixelvalues of the predictive block from the pixel values of the currentvideo block being coded, forming pixel difference values. In general,motion estimation component 221 performs motion estimation relative toluma components, and motion compensation component 219 uses motionvectors calculated based on the luma components for both chromacomponents and luma components. The predictive block and residual blockare forwarded to transform scaling and quantization component 213.

The partitioned video signal 201 is also sent to intra-pictureestimation component 215 and intra-picture prediction component 217. Aswith motion estimation component 221 and motion compensation component219, intra-picture estimation component 215 and intra-picture predictioncomponent 217 may be highly integrated, but are illustrated separatelyfor conceptual purposes. The intra-picture estimation component 215 andintra-picture prediction component 217 intra-predict a current blockrelative to blocks in a current frame, as an alternative to theinter-prediction performed by motion estimation component 221 and motioncompensation component 219 between frames, as described above. Inparticular, the intra-picture estimation component 215 determines anintra-prediction mode to use to encode a current block. In someexamples, intra-picture estimation component 215 selects an appropriateintra-prediction mode to encode a current block from multiple testedintra-prediction modes. The selected intra-prediction modes are thenforwarded to the header formatting and CABAC component 231 for encoding.

For example, the intra-picture estimation component 215 calculatesrate-distortion values using a rate-distortion analysis for the varioustested intra-prediction modes, and selects the intra-prediction modehaving the best rate-distortion characteristics among the tested modes.Rate-distortion analysis generally determines an amount of distortion(or error) between an encoded block and an original unencoded block thatwas encoded to produce the encoded block, as well as a bitrate (e.g., anumber of bits) used to produce the encoded block. The intra-pictureestimation component 215 calculates ratios from the distortions andrates for the various encoded blocks to determine which intra-predictionmode exhibits the best rate-distortion value for the block. In addition,intra-picture estimation component 215 may be configured to code depthblocks of a depth map using a DMM based on RDO.

The intra-picture prediction component 217 may generate a residual blockfrom the predictive block based on the selected intra-prediction modesdetermined by intra-picture estimation component 215 when implemented onan encoder or read the residual block from the bitstream whenimplemented on a decoder. The residual block includes the difference invalues between the predictive block and the original block, representedas a matrix. The residual block is then forwarded to the transformscaling and quantization component 213. The intra-picture estimationcomponent 215 and the intra-picture prediction component 217 may operateon both luma and chroma components.

The transform scaling and quantization component 213 is configured tofurther compress the residual block. The transform scaling andquantization component 213 applies a transform, such as a DCT, a DST, ora conceptually similar transform, to the residual block, producing avideo block comprising residual transform coefficient values. Wavelettransforms, integer transforms, sub-band transforms or other types oftransforms could also be used. The transform may convert the residualinformation from a pixel value domain to a transform domain, such as afrequency domain. The transform scaling and quantization component 213is also configured to scale the transformed residual information, forexample based on frequency. Such scaling involves applying a scalefactor to the residual information so that different frequencyinformation is quantized at different granularities, which may affectfinal visual quality of the reconstructed video. The transform scalingand quantization component 213 is also configured to quantize thetransform coefficients to further reduce bit rate. The quantizationprocess may reduce the bit depth associated with some or all of thecoefficients. The degree of quantization may be modified by adjusting aquantization parameter. In some examples, the transform scaling andquantization component 213 may then perform a scan of the matrixincluding the quantized transform coefficients. The quantized transformcoefficients are forwarded to the header formatting and CABAC component231 to be encoded in the bitstream.

The scaling and inverse transform component 229 applies a reverseoperation of the transform scaling and quantization component 213 tosupport motion estimation. The scaling and inverse transform component229 applies inverse scaling, transformation, and/or quantization toreconstruct the residual block in the pixel domain, e.g., for later useas a reference block which may become a predictive block for anothercurrent block. The motion estimation component 221 and/or motioncompensation component 219 may calculate a reference block by adding theresidual block back to a corresponding predictive block for use inmotion estimation of a later block/frame. Filters are applied to thereconstructed reference blocks to mitigate artifacts created duringscaling, quantization, and transform. Such artifacts could otherwisecause inaccurate prediction (and create additional artifacts) whensubsequent blocks are predicted.

The filter control analysis component 227 and the in-loop filterscomponent 225 apply the filters to the residual blocks and/or toreconstructed image blocks. For example, the transformed residual blockfrom the scaling and inverse transform component 229 may be combinedwith a corresponding prediction block from intra-picture predictioncomponent 217 and/or motion compensation component 219 to reconstructthe original image block. The filters may then be applied to thereconstructed image block. In some examples, the filters may instead beapplied to the residual blocks. As with other components in FIG. 2, thefilter control analysis component 227 and the in-loop filters component225 are highly integrated and may be implemented together, but aredepicted separately for conceptual purposes. Filters applied to thereconstructed reference blocks are applied to particular spatial regionsand include multiple parameters to adjust how such filters are applied.The filter control analysis component 227 analyzes the reconstructedreference blocks to determine where such filters should be applied andsets corresponding parameters. Such data is forwarded to the headerformatting and CABAC component 231 as filter control data for encoding.The in-loop filters component 225 applies such filters based on thefilter control data. The filters may include a deblocking filter, anoise suppression filter, a SAO filter, and an adaptive loop filter.Such filters may be applied in the spatial/pixel domain (e.g., on areconstructed pixel block) or in the frequency domain, depending on theexample.

When operating as an encoder, the filtered reconstructed image block,residual block, and/or prediction block are stored in the decodedpicture buffer component 223 for later use in motion estimation asdiscussed above. When operating as a decoder, the decoded picture buffercomponent 223 stores and forwards the reconstructed and filtered blockstoward a display as part of an output video signal. The decoded picturebuffer component 223 may be any memory device capable of storingprediction blocks, residual blocks, and/or reconstructed image blocks.

The header formatting and CABAC component 231 receives the data from thevarious components of codec system 200 and encodes such data into acoded bitstream for transmission toward a decoder. Specifically, theheader formatting and CABAC component 231 generates various headers toencode control data, such as general control data and filter controldata. Further, prediction data, including intra-prediction and motiondata, as well as residual data in the form of quantized transformcoefficient data are all encoded in the bitstream. The final bitstreamincludes all information desired by the decoder to reconstruct theoriginal partitioned video signal 201. Such information may also includeintra-prediction mode index tables (also referred to as codeword mappingtables), definitions of encoding contexts for various blocks,indications of most probable intra-prediction modes, an indication ofpartition information, etc. Such data may be encoded by employingentropy coding. For example, the information may be encoded by employingCAVLC, CABAC, SBAC, PIPE coding, or another entropy coding technique.Following the entropy coding, the coded bitstream may be transmitted toanother device (e.g., a video decoder) or archived for latertransmission or retrieval.

FIG. 3 is a block diagram illustrating an example video encoder 300.Video encoder 300 may be employed to implement the encoding functions ofcodec system 200 and/or implement steps 101, 103, 105, 107, and/or 109of operating method 100. Encoder 300 partitions an input video signal,resulting in a partitioned video signal 301, which is substantiallysimilar to the partitioned video signal 201. The partitioned videosignal 301 is then compressed and encoded into a bitstream by componentsof encoder 300.

Specifically, the partitioned video signal 301 is forwarded to anintra-picture prediction component 317 for intra-prediction. Theintra-picture prediction component 317 may be substantially similar tointra-picture estimation component 215 and intra-picture predictioncomponent 217. The partitioned video signal 301 is also forwarded to amotion compensation component 321 for inter-prediction based onreference blocks in a decoded picture buffer component 323. The motioncompensation component 321 may be substantially similar to motionestimation component 221 and motion compensation component 219. Theprediction blocks and residual blocks from the intra-picture predictioncomponent 317 and the motion compensation component 321 are forwarded toa transform and quantization component 313 for transform andquantization of the residual blocks. The transform and quantizationcomponent 313 may be substantially similar to the transform scaling andquantization component 213. The transformed and quantized residualblocks and the corresponding prediction blocks (along with associatedcontrol data) are forwarded to an entropy coding component 331 forcoding into a bitstream. The entropy coding component 331 may besubstantially similar to the header formatting and CABAC component 231.

The transformed and quantized residual blocks and/or the correspondingprediction blocks are also forwarded from the transform and quantizationcomponent 313 to an inverse transform and quantization component 329 forreconstruction into reference blocks for use by the motion compensationcomponent 321. The inverse transform and quantization component 329 maybe substantially similar to the scaling and inverse transform component229. In-loop filters in an in-loop filters component 325 are alsoapplied to the residual blocks and/or reconstructed reference blocks,depending on the example. The in-loop filters component 325 may besubstantially similar to the filter control analysis component 227 andthe in-loop filters component 225. The in-loop filters component 325 mayinclude multiple filters as discussed with respect to in-loop filterscomponent 225. The filtered blocks are then stored in a decoded picturebuffer component 323 for use as reference blocks by the motioncompensation component 321. The decoded picture buffer component 323 maybe substantially similar to the decoded picture buffer component 223.

FIG. 4 is a block diagram illustrating an example video decoder 400.Video decoder 400 may be employed to implement the decoding functions ofcodec system 200 and/or implement steps 111, 113, 115, and/or 117 ofoperating method 100. Decoder 400 receives a bitstream, for example froman encoder 300, and generates a reconstructed output video signal basedon the bitstream for display to an end user.

The bitstream is received by an entropy decoding component 433. Theentropy decoding component 433 is configured to implement an entropydecoding scheme, such as CAVLC, CABAC, SBAC, PIPE coding, or otherentropy coding techniques. For example, the entropy decoding component433 may employ header information to provide a context to interpretadditional data encoded as codewords in the bitstream. The decodedinformation includes any desired information to decode the video signal,such as general control data, filter control data, partitioninformation, motion data, prediction data, and quantized transformcoefficients from residual blocks. The quantized transform coefficientsare forwarded to an inverse transform and quantization component 429 forreconstruction into residual blocks. The inverse transform andquantization component 429 may be similar to inverse transform andquantization component 329.

The reconstructed residual blocks and/or prediction blocks are forwardedto intra-picture prediction component 417 for reconstruction into imageblocks based on intra-prediction operations. The intra-pictureprediction component 417 may be similar to intra-picture estimationcomponent 215 and an intra-picture prediction component 217.Specifically, the intra-picture prediction component 417 employsprediction modes to locate a reference block in the frame and applies aresidual block to the result to reconstruct intra-predicted imageblocks. The reconstructed intra-predicted image blocks and/or theresidual blocks and corresponding inter-prediction data are forwarded toa decoded picture buffer component 423 via an in-loop filters component425, which may be substantially similar to decoded picture buffercomponent 223 and in-loop filters component 225, respectively. Thein-loop filters component 425 filters the reconstructed image blocks,residual blocks and/or prediction blocks, and such information is storedin the decoded picture buffer component 423. Reconstructed image blocksfrom decoded picture buffer component 423 are forwarded to a motioncompensation component 421 for inter-prediction. The motion compensationcomponent 421 may be substantially similar to motion estimationcomponent 221 and/or motion compensation component 219. Specifically,the motion compensation component 421 employs motion vectors from areference block to generate a prediction block and applies a residualblock to the result to reconstruct an image block. The resultingreconstructed blocks may also be forwarded via the in-loop filterscomponent 425 to the decoded picture buffer component 423. The decodedpicture buffer component 423 continues to store additional reconstructedimage blocks, which can be reconstructed into frames via the partitioninformation. Such frames may also be placed in a sequence. The sequenceis output toward a display as a reconstructed output video signal.

FIG. 5 is an example of point cloud media 500 that can be codedaccording to PCC mechanisms. Accordingly, point cloud media 500 may becoded by an encoder, such as codec system 200 and/or encoder 300, andreconstructed by a decoder, such as codec system 200 and/or decoder 400,when performing method 100.

The mechanisms described in FIGS. 1-4 generally presume a 2D frame isbeing coded. However, point cloud media 500 is a cloud of points thatchange over time. Specifically, the point cloud media 500, which canalso be referred to as a point cloud and/or a point cloudrepresentation, is group of points in 3D space. The points may also bereferred to as samples. Each point may be associated with multiple typesof data. For example, each point may be described in terms of position.Position is a location in 3D space that may be described as a set ofCartesian coordinates. Further, each point may contain a color. Colormay be described in terms of luminance (e.g., light) and chrominance(e.g., color). Color may be described in terms of (R), green (G), andblue (B) values, or luma (Y), blue projection (U), and red projection(V), denoted as (R, G, B) or (Y, U, V), respectively. The points mayalso include other attributes. An attribute is an optional scalar or avector property that may be associated with each point in a point cloud.Attributes may include reflectance, transparency, surface normal, timestamps, and material ID.

As each point in a point cloud media 500 may be associated with multipletypes of data, several supporting mechanisms are employed to prepare thepoint cloud media 500 for compression according to the mechanismsdescribed in FIGS. 1-4. For example, the point cloud media 500 can besorted into frames, where each frame includes all the data related to apoint cloud for a particular state or instant in time. As such, FIG. 5depicts a single frame of the point cloud media 500. The point cloudmedia 500 is then coded on a frame by frame basis. The point cloud media500 can be surrounded by a 3D bounding box 501. The 3D bounding box 501is a 3D rectangular prism that is sized to surround all of the points ofthe point cloud media 500 for the corresponding frame. It should benoted that multiple 3D bounding boxes 501 may be employed in the eventthat the point cloud media 500 includes disjoint sets. For example, thepoint cloud media 500 could depict two figures that are not connected,in which case a 3D bounding box 501 would be placed around each figure.The points in the 3D bounding box 501 are processed as described below.

FIG. 6 is an example of patches 603 created from a point cloud 600.Point cloud 600 is a single frame of point cloud media 500. Further,point cloud 600 is surrounded by a 3D bounding box 601 that issubstantially similar to 3D bounding box 501. Accordingly, point cloud600 may be coded by an encoder, such as codec system 200 and/or encoder300, and reconstructed by a decoder, such as codec system 200 and/ordecoder 400, when performing method 100.

The 3D bounding box 601 includes six faces, and hence includes six 2Drectangular frames 602 that are each positioned at a face of the 3Dbounding box 601 (e.g., top, bottom, left, right, front, and back). Thepoint cloud 600 can be converted from 3D data into 2D data by projectingthe point cloud 600 onto the corresponding 2D rectangular frames 602.This results in the creation of patches 603. A patch 603 is a 2Drepresentation of a 3D point cloud, where the patch 603 contains arepresentation of the point cloud 600 that is visible from thecorresponding 2D rectangular frame 602. It should be noted that arepresentation of the point cloud 600 from a 2D rectangular frame 602may contain multiple disjoint components. As such, a 2D rectangularframe 602 may contain a plurality of patches 603. As such, a point cloud600 may be represented by more than six patches 603. The patches 603 mayalso be referred to as atlas, atlas data, atlas information, and/oratlas components. By converting the 3D data into a 2D format, the pointcloud 600 can be coded according to video coding mechanisms, such asinter-prediction and/or intra-prediction.

FIGS. 7A-7C illustrate mechanisms for encoding a 3D point cloud that hasbeen converted into 2D information as described in FIG. 6. Specifically,FIG. 7A illustrates an example occupancy frame 710 associated with a setof patches, such as patches 603. The occupancy frame 710 is coded inbinary form. For example, a zero represents that a portion of thebounding box 601 is not occupied by one of the patches 603. Thoseportions of the bounding box 601 represented by the zeros do not takepart in reconstruction of a volumetric representation (e.g., the pointcloud 600). In contrast, a one represents that a portion of the boundingbox 601 is occupied by one of the patches 603. Those portions of thebounding box 601 represented by the ones do take part in reconstructionof the volumetric representation (e.g., the point cloud 600). Further,FIG. 7B illustrates an example geometry frame 720 associated with a setof patches, such as patches 603. The geometry frame 720 provides ordepicts the contour or topography of each of the patches 603.Specifically, the geometry frame 720 indicates the distance that eachpoint in the patches 603 is away from the planar surface (e.g., the 2Drectangular frame 602) of the bounding box 601. Also, FIG. 7Cillustrates an example atlas frame 730 associated with a set of patches,such as patches 603. The atlas frame 730 provides or depicts samples ofthe patches 603 in the bounding box 601. The atlas frame 730 mayinclude, for example, a color component of the points in the patches603. The color component may be based on the RGB color model or anothercolor model. The occupancy frame 710, geometry frame 720, and atlasframe 730 can be employed to code a point cloud 600 and/or point cloudmedia 500. As such, the occupancy frame 710, geometry frame 720, andatlas frame 730 may be coded by an encoder, such as codec system 200and/or encoder 300, and reconstructed by a decoder, such as codec system200 and/or decoder 400, when performing method 100.

The various patches created by projecting 3D information onto 2D planescan be packed into a rectangular (or square) video frame. This approachmay be advantageous because various video codecs are preconfigured tocode such video frames. As such, the PCC codec can employ other videocodecs to code the patches. As shown in FIG. 7A, the patches can bepacked into a frame. The patches may be packed by any algorithm. Forexample, the patches can be packed into the frame based on size. In aparticular example, the patches are included from largest to smallest.The largest patches may be placed first in any open space, with smallerpatches filling in gaps once a size threshold has been crossed. As shownin FIG. 7A, such a packing scheme results in blank space that does notinclude patch data. To avoid encoding blank space, an occupancy frame710 is employed. An occupancy frame 710 contains all occupancy data fora point cloud at a particular instant in time. Specifically, theoccupancy frame 710 contains one or more occupancy maps (also known asoccupancy data, occupancy information, and/or occupancy components). Anoccupancy map is defined as a 2D array corresponding to an atlas (groupof patches) whose values indicate, for each sample position in theatlas, whether that position corresponds to a valid 3D point in thepoint cloud representation. As shown in FIG. 7A, the occupancy mapsinclude areas of valid data 713. The areas of valid data 713 indicatethat atlas/patch data is present in corresponding locations in theoccupancy frame 710. The occupancy maps also include areas of invaliddata 715. The areas of invalid data 715 indicate that atlas/patch datais not present in corresponding locations in the occupancy frame 710.

FIG. 7B depicts a geometry frame 720 of the point cloud data. Thegeometry frame 720 contains one or more geometry maps 723 (also known asgeometry data, geometry information, and/or geometry components) for apoint cloud at a particular instant in time. A geometry map 723 is a 2Darray created through the aggregation of the geometry informationassociated with each patch, where geometry information/data is a set ofCartesian coordinates associated with a point cloud frame. Specifically,the patches are all projected from points in 3D space. Such projectionhas the effect of removing the 3D information from the patches. Thegeometry map 723 retains the 3D information removed from the patches.For example, each sample in a patch is obtained from a point in 3Dspace. Accordingly, the geometry map 723 may include a 3D coordinateassociated with each sample in each patch. Hence, the geometry map 723can be used by a decoder to map/convert the 2D patches back into 3Dspace to reconstruct the 3D point cloud. Specifically, the decoder canmap each patch sample onto the appropriate 3D coordinate to reconstructthe point cloud.

FIG. 7C depicts an atlas frame 730 of the point cloud data. The atlasframe 730 contains one or more atlas 733 (also known as atlas data,atlas information, atlas components, and/or patches) for a point cloudat a particular instant in time. An atlas 733 is a collection of 2Dbounding boxes projected into rectangular frames that correspond to a 3Dbounding box in 3D space, where each 2D bounding box/patch represents asubset of a point cloud. Specifically, the atlas 733 contains patchescreated when the 3D point cloud is projected into 2D space as describedwith respect to FIG. 6. As such, the atlas 733/patches contain the imagedata (e.g., the color and light values) associated with the point cloudand a corresponding instant in time. The atlas 733 corresponds to theoccupancy map of FIG. 7A and the geometry map 723 of FIG. 7B.Specifically, the atlas 733 contains data in areas of valid data 713,and does not contain data in the areas of invalid data 715. Further, thegeometry map 723 contains the 3D information for the samples in theatlas 733.

It should also be noted that a point cloud can contain attributes (alsoknown as attribute data, attribute information, and/or attributecomponents). Such attributes can be included in an atlas frame. An atlasframe may contain all data regarding a corresponding attribute of thepoint cloud at a particular instant in time. An example of an attributeframe is not shown as attributes may include a wide range of differentdata. Specifically, an attribute may be any scalar or vector propertyassociated with each point in a point cloud such as reflectance, surfacenormal, time stamps, material IDs, etc. Further, attributes are optional(e.g., user defined), and may vary based on application. However, whenused, the point cloud attributes may be included in an attribute framein a manner similar to the atlas 733, geometry map 723, and occupancymaps.

Accordingly, an encoder can compress a point cloud frame into an atlasframe 730 of atlas 733, a geometry frame 720 of geometry maps 723, anoccupancy frame 710 of occupancy maps, and optionally an attribute frameof attributes. The atlas frame 730, geometry frame 720, occupancy frame710, and/or attribute frame can be further compressed, for example bydifferent encoders for transmission to a decoder. The decoder candecompress the atlas frame 730, geometry frame 720, occupancy frame 710,and/or attribute frame. The decoder can then employ the atlas frame 730,geometry frame 720, occupancy frame 710, and/or attribute frame toreconstruct the point cloud frame to determine a reconstructed pointcloud at a corresponding instant of time. The reconstructed point cloudframes can then be included in sequence to reconstruct the originalpoint cloud sequence (e.g., for display and/or for use in dataanalysis). As a particular example, the atlas frame 730 and/or atlas 733may be encoded and decoded by employing the techniques described withrespect to FIGS. 1-4, for example by employing a VVC, HEVC, and/or AVCcodec.

FIG. 8 is a schematic diagram of an example conformance testingmechanism 800. The conformance testing mechanism 800 may be employed byan encoder, such as a codec system 200 and/or an encoder 300, to verifythat a PCC bitstream conforms with standards, and hence can be decodedby a decoder, such as a codec system 200 and/or a decoder 400. Forexample, the conformance testing mechanism 800 may be employed to checkwhether a point cloud media 500 and/or patches 603 have been coded intoan occupancy frame 710, a geometry frame 720, an atlas frame 730, and/oran attribute frame in a manner that can be correctly decoded whenperforming method 100.

The conformance testing mechanism 800 can test a PCC bitstream forconformance with standards. A PCC bitstream that conforms with standardsshould always be decodable by any decoder that also conforms tostandards. A PCC bitstream that does not conform with standards may notbe decodable. Hence, a PCC bitstream that fails conformance testingmechanism 800 should be re-encoded, for example by using differentsettings. The conformance testing mechanism 800 includes a type Iconformance test 881 and a type II conformance test 883, which may alsobe referred to as conformance point A and B, respectively. A type Iconformance test 881 checks the components of a PCC bitstream forconformance. A type II conformance test 883 checks a reconstructed pointcloud for conformance. An encoder is generally required to perform atype I conformance test 881 and may optionally perform a type IIconformance test 883.

Prior to performing conformance testing mechanism 800, the encoderencodes a compressed V-PCC bitstream 801 as described above. The encodermay then employ a HRD to perform the conformance testing mechanism 800on the compressed V-PCC bitstream 801. The conformance testing mechanism800 separates the compressed V-PCC bitstream 801 into components.Specifically, the compressed V-PCC bitstream 801 is split into acompressed atlas sub-bitstream 830, a compressed occupancy mapsub-bitstream 810, a compressed geometry sub-bitstream 820, andoptionally a compressed attribute sub-bitstream 840, which containsequences of coded atlas frames 730, coded geometry frames 720,occupancy frames 710, and optionally attribute frames, respectively.

Entropy decompression or video decompression 860 is performed on thesub-streams. Entropy decompression or video decompression 860 is amechanism of reversing the component specific compression. Thecompressed atlas sub-bitstream 830, compressed occupancy mapsub-bitstream 810, compressed geometry sub-bitstream 820, and compressedattribute sub-bitstream 840 may be encoded by one or more codecs, andhence entropy decompression or video decompression 860 includes applyinga hypothetical decoder to each sub-bitstream based on the encoderemployed to create the corresponding sub-bitstream. The entropydecompression or video decompression 860 reconstructs a decompressedatlas sub-bitstream 831, decompressed occupancy map sub-bitstream 811,decompressed geometry sub-bitstream 821, and decompressed attributesub-bitstream 841 from the compressed atlas sub-bitstream 830,compressed occupancy map sub-bitstream 810, compressed geometrysub-bitstream 820, and compressed attribute sub-bitstream 840,respectively. A decompressed sub-bitstream/component is data from asub-bitstream that has been reconstructed as part of a decoding processor, in this case, as part of a HRD conformance test.

A type I conformance test 881 is applied to the decompressed atlassub-bitstream 831, decompressed occupancy map sub-bitstream 811,decompressed geometry sub-bitstream 821, and decompressed attributesub-bitstream 841. The type I conformance test 881 checks each component(the decompressed atlas sub-bitstream 831, decompressed occupancy mapsub-bitstream 811, decompressed geometry sub-bitstream 821, anddecompressed attribute sub-bitstream 841) to ensure the correspondingcomponent complies with the standard used by the codec to encode anddecode that component. For example, the type I conformance test 881 canverify that a standardized amount of hardware resources are capable ofdecompressing the corresponding component without buffer over-runs orunder-runs. Further, the type I conformance test 881 can check thecomponents for coding errors that prevent the HRD from correctlyreconstructing the corresponding components. In addition, the type Iconformance test 881 can check each corresponding component to ensurethat all standard requirements are met and that all standardprohibitions are omitted. The type I conformance test 881 is satisfiedwhen all components pass the corresponding tests, and is not satisfiedwhen any one of the components fails a corresponding test. Any componentthat passes the type I conformance test 881 should be decodable at anydecoder that also complies with the corresponding standards. As such,the type I conformance test 881 may be utilized when encoding acompressed V-PCC bitstream 801.

While a type I conformance test 881 ensures that components aredecodable, the type I conformance test 881 does not guarantee that adecoder can reconstruct the original point cloud from the correspondingcomponents. Accordingly, conformance testing mechanism 800 may also beemployed to perform a type II conformance test 883. The decompressedoccupancy map sub-bitstream 811, decompressed geometry sub-bitstream821, and decompressed attribute sub-bitstream 841 are forwarded forconversion 861. Specifically, conversion 861 may convert the chromaformat, resolution, and/or the frame rate of the decompressed occupancymap sub-bitstream 811, decompressed geometry sub-bitstream 821, anddecompressed attribute sub-bitstream 841 as desired to match the chromaformat, resolution, and/or the frame rate of the decompressed atlassub-bitstream 831.

The results of conversion 861 as well as the decompressed atlassub-bitstream 831 are forwarded to geometry reconstruction 862. Atgeometry reconstruction 862, the occupancy maps from the decompressedoccupancy map sub-bitstream 811 are employed to determine the locationsof valid atlas data. The geometry reconstruction 862 can then obtaingeometry data from the decompressed geometry sub-bitstream 821 from anylocation that contains valid atlas data. The geometry data can then beemployed to reconstruct a rough cloud of points, which is forwarded toduplicate point removal 863. For example, during the creation of 2Dpatches from a 3D cloud, some cloud points can be viewed from multipledirections. When this happens, the same point is projected as a sampleinto more than one patch. The geometry data is then generated based onsamples, and hence includes duplicate data for such points. Theduplicate point removal 863 merges such duplicate data to create asingle point when geometry data indicates multiple points are located atthe same location. The result is a reconstructed geometry 871 thatmirrors the geometry of the originally encoded point cloud.Specifically, the reconstructed geometry 871 includes the 3D position ofeach point from the encoded point cloud.

The reconstructed geometry 871 is forwarded for smoothing 864.Specifically, the reconstructed geometry 871 may contain certainfeatures that appear sharp due to noise created during the codingprocess. Smoothing 864 may employ one or more filters to remove suchnoise in order to create a smoothed geometry 873 that is an accuraterepresentation of the originally encoded point cloud. The smoothedgeometry 873 is then forwarded to attribute reconstruction 865 alongwith atlas data from the decompressed atlas sub-bitstream 831 andattribute data from conversion 861. Attribute reconstruction 865 colorsthe points located at the smoothed geometry 873 with the colors from theatlas/patch data. Attribute reconstruction 865 also applies anyattributes to the points. This results in a reconstructed cloud 875 thatmirrors the originally encoded point cloud. The reconstructed cloud 875may contain color or other attribute noise caused by the coding process.Accordingly, the reconstructed cloud 875 is forwarded for colorsmoothing 866, which applies one or more filters to the luma, chroma, orother attribute values to smooth such noise. Color smoothing 866 canthen output a reconstructed point cloud 877. The reconstructed pointcloud 877 should be an exact representation of the originally encodedpoint cloud if lossless coding is employed. Otherwise, the reconstructedpoint cloud 877 closely approximates the originally encoded point cloudwith variances that do not exceed a predefined tolerance.

The type II conformance test 883 is applied to the reconstructed pointcloud 877. The Type II conformance test 883 checks the reconstructedpoint cloud 877 to ensure the reconstructed point cloud 877 complieswith the V-PCC standard, and hence can be decoded by a decoder thatcomplies with the V-PCC standard. For example, the type II conformancetest 883 can verify that a standardized amount of hardware resources arecapable of reconstructing the reconstructed point cloud 877 withoutbuffer over-runs or under-runs. Further, the type II conformance test883 can check the reconstructed point cloud 877 for coding errors thatprevent the HRD from correctly reconstructing the reconstructed pointcloud 877. In addition, the type II conformance test 883 can check eachdecompressed component and/or any intermediate data to ensure that allstandard requirements are met and that all standard prohibitions areomitted. The type II conformance test 883 is satisfied when thereconstructed point cloud 877 and any intermediate components pass thecorresponding tests, and is not satisfied when the reconstructed pointcloud 877 or any of the intermediate components fails a correspondingtest. When the reconstructed point cloud 877 passes the type IIconformance test 883, the reconstructed point cloud 877 should bedecodable at any decoder that also complies with the V-PCC standard. Assuch, the type II conformance test 883 may provide a more robustverification of the compressed V-PCC bitstream 801 than the type Iconformance test 881.

FIG. 9 is a schematic diagram of an example HRD 900 configured toperform a conformance test, for example by employing conformance testingmechanism 800, on a PCC bitstream, which may include a point cloud media500 and/or patches 603 coded into an occupancy frame 710, a geometryframe 720, an atlas frame 730, and/or an attribute frame. As such, theHRD 900 may be employed by a codec system 200 and/or an encoder 300 thatis encoding a bitstream as part of method 100 for decoding by a codecsystem 200 and/or decoder 400. Specifically, the HRD 900 may check a PCCbitstream and/or components thereof before the PCC bitstream isforwarded to a decoder. In some examples, the PCC bitstream may becontinuously forwarded through the HRD 900 as the PCC bitstream isencoded. In the event that a portion of the PCC bitstream fails toconform to associated constraints, the HRD 900 can indicate such failureto an encoder, which may cause the encoder to re-encode thecorresponding section of the bitstream with different mechanisms. Insome examples, the HRD 900 may be configured to perform checks on anatlas sub-bitstream and/or on a reconstructed point cloud. In someexamples, the occupancy map components, geometry components, andattribute components may be encoded by other codecs. Hence, thesub-bitstreams containing the occupancy map components, geometrycomponents, and attribute components may be checked by other HRDs. Assuch, a plurality of HRDs that include HRD 900 may be employed tocompletely check a PCC bitstream for conformance in some examples.

The HRD 900 includes an HSS 941. A HSS 941 is a component configured toperform a hypothetical delivery mechanism. The hypothetical deliverymechanism is used for checking the conformance of a bitstream, asub-bitstream, and/or a decoder with regards to the timing and data flowof a PCC bitstream 951 input into the HRD 900. For example, the HSS 941may receive a PCC bitstream 951 or a sub-bitstream thereof output froman encoder. The HSS 941 may then manage the conformance testing processon the PCC bitstream 951, for example by employing conformance testingmechanism 800. In a particular example, the HSS 941 can control the ratethat coded atlas data moves through the HRD 900 and verify that the PCCbitstream 951 does not contain non-conforming data. The HSS 941 mayforward the PCC bitstream 951 to a CAB 943 at a predefined rate. Forpurposes of the HRD 900, any units containing coded video in the PCCbitstream 951, such as an AU and/or a NAL unit, may be referred to asdecoding atlas units 953. Decoding atlas units 953 may contain onlyatlas data in some examples. In other examples, the decoding atlas units953 may contain other PCC components and/or a set of data to reconstructthe point cloud. Accordingly, the decoding atlas units 953 may generallybe referred to as decoding units in same examples. The CAB 943 is a FIFObuffer in the HRD 900. The CAB 943 contains decoding atlas units 953including atlas data, geometry data, occupancy data, and/or attributedata, in decoding order. The CAB 943 stores such data for use during PCCbitstream conformance testing/checking.

The CAB 943 forwards the decoding atlas units 953 to a decoding processcomponent 945. The decoding process component 945 is a component thatconforms to a PCC standard or other standard employed to code a PCCbitstream and/or sub-bitstream thereof. For example, the decodingprocess component 945 may emulate a decoder employed by an end user. Forexample, the decoding process component 945 may perform a type Iconformance test by decoding atlas components and/or a type IIconformance test by reconstructing point cloud data. The decodingprocess component 945 decodes the decoding atlas units 953 at a ratethat can be achieved by an example standardized decoder. If the decodingprocess component 945 cannot decode the decoding atlas units 953 fastenough to prevent an overflow of the CAB 943, then the PCC bitstream 951does not conform to the standard and should be re-encoded. Likewise, ifthe decoding process component 945 decodes the decoding atlas units 953too quickly and the CAB 943 runs out of data (e.g., a buffer underrun),then the PCC bitstream 951 does not conform to the standard and shouldbe re-encoded.

The decoding process component 945 decodes the decoding atlas units 953,which creates decoded atlas frames 955. Decoded atlas frames 955 maycontain a complete set of atlas data for a PCC frame in the event of atype I conformance test or a frame of a reconstructed point cloud in atype II conformance test context. The decoded atlas frames 955 areforwarded to a DAB 947. The DAB 947 is a FIFO buffer in a HRD 900 thatcontains decoded/decompressed atlas frames and/or reconstructed pointcloud frames (depending on context) in decoding order for use during PCCbitstream conformance testing. The DAB 947 may be substantially similarto a decoded picture buffer component 223, 323, and/or 423. To supportinter-prediction, frames that are marked for use as reference atlasframes 956 that are obtained from the decoded atlas frames 955 arereturned to the decoding process component 945 to support furtherdecoding. The DAB 947 outputs the atlas data 957 (or reconstructed pointclouds, depending on context) on a frame by frame basis. As such, theHRD 900 can determine whether coding is satisfactory and whetherconstraints are met by the PCC bitstream 951 and/or components thereof.

FIG. 10 is a schematic diagram illustrating an example PCC bitstream1000 for use in initializing a HRD, such as HRD 900, to support HRDconformance tests, such as conformance testing mechanism 800. Forexample, the bitstream 1000 can be generated by a codec system 200and/or an encoder 300 for decoding by a codec system 200 and/or adecoder 400 according to method 100. Further, the bitstream 1000 mayinclude a point cloud media 500 and/or patches 603 coded into anoccupancy frame 710, a geometry frame 720, an atlas frame 730, and/or anattribute frame. In addition, bitstream 1000 can be checked forconformance by a HRD, such as HRD 900, employing conformance testingmechanisms such as conformance testing mechanism 800.

The PCC bitstream 1000 includes a sequence of PCC AUs 1010. A PCC AU1010 includes sufficient components to reconstruct a single PCC framecaptured at a particular time instance. For example, a PCC AU 1010 maycontain an atlas frame 1011, an occupancy map frame 1013, and a geometrymap frame 1015, which may be substantially similar to an atlas frame730, an occupancy frame 710, and a geometry frame 720, respectively. ThePCC AU 1010 may also contain an attribute frame 1017, which includes allof the attributes related to the point cloud at the time instance ascoded in the PCC AU 1010. Such attributes may include a scalar or vectorproperty optionally associated with each point in a point cloud such ascolor, reflectance, surface normal, time stamps, material ID, etc. A PCCAU 1010 may be defined as a set of NAL units that are associated witheach other according to a specified classification rule and pertain toone particular output time. As such, data is positioned in the PCC AUs1010 in NAL units. A NAL unit is a packet sized data container. Forexample, a single NAL unit is generally sized to allow for networktransmission. A NAL unit may contain a header indicating the NAL unittype and a payload that contains the associated data.

The PCC bitstream 1000 also includes various data structures to supportdecoding the PCC AUs 1010, for example as part of a decoding processand/or as part of a HRD process. For example, the PCC bitstream 1000 mayinclude various parameter sets that contain parameters used to code theone or more PCC AUs 1010. As a specific example, the PCC bitstream 1000may contain an atlas SPS 1020. An atlas SPS 1020 is a syntax structurecontaining syntax elements that apply to zero or more entire coded atlassequences as determined by the content of a syntax element found in theatlas SPS 1020 referred to by a syntax element found in each tile groupheader. For example, the atlas SPS 1020 may contain parameters that arerelated to an entire sequence of atlas frames 1011.

The PCC bitstream 1000 also includes various SEI messages. An SEImessage is a syntax structure with specified semantics that conveysinformation that is not needed by decoding processes in order todetermine the values of samples in decoded pictures. Accordingly, SEImessages may be employed to convey data that is not directly related todecoding PCC AUs 1010. In the example shown, the PCC bitstream 1000includes a buffering period SEI message 1030 and an atlas frame timingSEI message 1040.

In the example shown, the atlas SPS 1020, buffering period SEI message1030, and the atlas frame timing SEI message 1040 are employed toinitialize and manage the function of a HRD when performing conformancetesting on a PCC bitstream 1000. For example, HRD parameters 1021 may beincluded in the atlas SPS 1020. The HRD parameters 1021 are syntaxelements that initialize and/or define operational conditions of a HRD.For example, the HRD parameters 1021 may be employed to specify aconformance point, such as a type I conformance test 881 or a type IIconformance test 883, for a HRD conformance check at the HRD. As suchthe HRD parameters 1021 may be employed to indicate whether an HRDconformance check should be performed on decompressed PCC components orreconstructed point clouds. For example, the HRD parameters 1021 may beset to a first value to indicate that a HRD conformance check should beperformed on decompressed attribute components, decompressed atlascomponents, decompressed occupancy map components, and decompressedgeometry components (e.g., the attribute frame 1017, the atlas frame1011, the occupancy map frame 1013, and the geometry map frame 1015,respectively.) Further, the HRD parameters 1021 may be set to a firstvalue to indicate that a HRD conformance check should be performed onreconstructed point clouds from the PCC components (e.g., reconstructedfrom the entire PCC AU 1010).

The buffering period SEI message 1030 is an SEI message that containsdata indicating initial removal delays related to a CAB (e.g., CAB 943)in a HRD. An initial CAB removal delay is an amount of time a componentin a first AU in a bitstream, such as a PCC AU 1010, or a first AU in asub-bitstream, such as an atlas frame 1011, can remain in the CAB priorto removal. For example, the HRD can begin removing any decoding unitsrelated to the first PCC AU 1010 from the CAB in the HRD during the HRDconformance check based on an initial delay specified by the bufferingperiod SEI message 1030. As such, the buffering period SEI message 1030contains data sufficient to initialize a HRD conformance testing processto begin at a coded PCC AU 1010 associated with the buffering period SEImessage 1030. Specifically, the buffering period SEI message 1030 mayindicate to the HRD that conformance testing should begin at the firstPCC AU 1010 in the PCC bitstream 1000.

The atlas frame timing SEI message 1040 is an SEI message that containsdata indicating a removal delay relating to a CAB (e.g., CAB 943) and anoutput delay related to a DAB (e.g., DAB 947) in a HRD. A CAB removaldelay is an amount of time a component (e.g., any correspondingcomponent) can remain in the CAB prior to removal. The CAB removal delaymay be coded in reference to the initial CAB removal delay indicated bythe buffering period SEI message 1030. A DAB output delay is an amountof time a decompressed/decoded component (e.g., any correspondingcomponent) can remain in the DAB prior to being output (e.g., as part ofa reconstructed point cloud). As such, a HRD may remove decoding unitsfrom the CAB in the HRD during conformance checks as specified by theatlas frame timing SEI message 1040. Further, a HRD can set an outputdelay of a DAB in the HRD as specified by the atlas frame timing SEImessage 1040.

Accordingly, the encoder can encode the HRD parameters 1021, bufferingperiod SEI message 1030, and the atlas frame timing SEI message 1040into the PCC bitstream 1000 during the encoding process. The HRD canthen read the HRD parameters 1021, buffering period SEI message 1030,and the atlas frame timing SEI message 1040 to obtain sufficientinformation to perform a conformance check, such as conformance testingmechanism 800, on the PCC bitstream 1000. Further, a decoder obtain theHRD parameters 1021, buffering period SEI message 1030, and/or the atlasframe timing SEI message 1040 from the PCC bitstream 1000 and infer bythe presence of such data that a HRD check has been performed on the PCCbitstream 1000. Hence, the decoder can infer that the PCC bitstream 1000is decodable, and hence can decode the PCC bitstream 1000 based on theHRD parameters 1021, buffering period SEI message 1030, and/or the atlasframe timing SEI message 1040.

The PCC bitstream 1000 may be of varying sizes and may be transmittedfrom an encoder to a decoder via a transmission network at variousrates. For example, an volumetric sequence that is approximately onehour in length can be encoded into a PCC bitstream 1000 with a file sizeof between fifteen and seventy gigabytes when an HEVC based encoder isemployed. A VVC based encoder may further reduce the file size by aboutthirty to thirty five percent versus the HEVC encoder. Accordingly, avolumetric sequence of an hour in length that is encoded with a VVCencoder may result in a file with a size of about ten to forty ninegigabytes. The PCC bitstream 1000 may be transmitted at different ratesdepending on the status of the transmission network. For example, a PCCbitstream 1000 may be transmitted across a network at a bit rate ofbetween five to twenty megabytes per second. Similarly, encoding anddecoding processes described herein can be performed, for example, atrates faster than one megabyte per second.

FIG. 11 is a schematic diagram of an example video coding device 1100.The video coding device 1100 is suitable for implementing the disclosedembodiments. The video coding device 1100 comprises downstream ports1120, upstream ports 1150, and TX/RXs 1110, including transmitters ortransmitting means and including receivers or receiving means forcommunicating data over a network. The video coding device 1100 alsoincludes a processor 1130 or processing means including a logic unit orCPU to process the data and a memory 1132 or storage means for storingthe data. The video coding device 1100 may also comprise electrical, OEcomponents, EO components, or wireless communication components coupledto the upstream ports 1150 or downstream ports 1120 for communication ofdata via electrical, optical, or wireless communication networks. Thevideo coding device 1100 may also include I/O devices 1160 forcommunicating data to and from a user. The I/O devices 1160 may includeoutput devices such as a display for displaying video data, speakers foroutputting audio data, etc. The I/O devices 1160 may also include inputdevices, such as a keyboard, mouse, trackball, etc., and/orcorresponding interfaces for interacting with such output devices.

The processor 1130 is implemented by hardware and software. Theprocessor 1130 may be implemented as one or more CPU chips, cores (e.g.,as a multi-core processor), FPGAs, ASICs, and DSPs. The processor 1130is in communication with the downstream ports 1120, Tx/Rx 1110, upstreamports 1150, and memory 1132. The processor 1130 comprises a codingmodule 1114. The coding module 1114 implements the disclosed embodimentsdescribed herein, such as methods 100, 1200, and 1300, which may employpoint cloud media 500 separated into a set of patches 603 and encodedinto an occupancy frame 710, a geometry frame 720, and an atlas frame730 in a PCC bitstream 1000. Further, the coding module 1114 mayimplement a HRD 900 that performs a conformance testing mechanism 800 onthe PCC bitstream 1000. The coding module 1114 may also implement anyother method/mechanism described herein. Further, the coding module 1114may implement a codec system 200, an encoder 300, and/or a decoder 400.Alternatively, the coding module 1114 can be implemented as instructionsstored in the memory 1132 and executed by the processor 1130 (e.g., as acomputer program product stored on a non-transitory medium).

The memory 1132 comprises one or more memory types such as disks, tapedrives, solid-state drives, ROM, RAM, flash memory, TCAM, SRAM, etc. Thememory 1132 may be used as an over-flow data storage device, to storeprograms when such programs are selected for execution, and to storeinstructions and data that are read during program execution.

A point cloud is a volumetric representation of space on a regular 3Dgrid. A voxel in a point cloud has x, y, and z coordinates and may haveRGB color components, reflectance, or other attributes. The datarepresentation in V-PCC relies on 3D-to-2D conversion and is describedas a set of planar 2D images with four types of data, which are referredto as components: occupancy maps, geometry data, attribute data, andatlas frames. An occupancy map is a binary image indication of occupiedor unoccupied blocks in the 2D projection. Geometry data are a heightmap for patch data, which describes per-point differences in distancesfrom the patch projection plane. Attribute data are 2D texture maps ofcorresponding components that represent attribute values atcorresponding 3D points of the point cloud. An atlas frame is metadatainformation that is required to perform 2d-to-3D conversion.

Atlas frames are missing information needed for V-PCC bitstreamsub-component synchronization and buffering. Specifically, when thebuffering process is implemented without the appropriate bufferingmodel, the decoded information has to be stored in an undefined memorylocation. The size of the memory needed may be a limitation on thedecoding device. There is therefore a desire to limit the needed buffermemory size.

Disclosed herein are embodiments for V-PCC component synchronization.The embodiments provide for a schema in which decoded V-PCC componentsare output at a corresponding component decoder, referred to as CP A,and are transferred to the buffer, where the synchronization process isimplemented in order to prepare the data to for reconstruction at CP B.An output delay synchronization is used in the synchronization process.The output delay synchronization improves synchronization, which reducesthe buffer memory size.

FIG. 12 is a schematic diagram 1200 of component synchronization inpoint cloud reconstruction. The schematic diagram 1200 shows V-PCCcomponents 1210, which may include an occupancy map, geometry data,attribute data, and an atlas frame, that arrive from a bitstream. AfterCP A, each V-PCC component 1210 is delayed for a period of an outputdelay synchronization 1220 corresponding to the V-PCC component 1210.The V-PCC components 1210 are then buffered in a V-PCC unit buffer 1230and undergo PCC reconstruction 1240. Finally, at CP B, the reconstructedpoint cloud 1250 is output.

The output delay synchronization 1220 may be calculated differently whenthe number of maps is 1 and when the number of maps is N. When thenumber of maps is 1, a DAB/DPB output time delay in a picture/atlas attiming SEI of access unit n is modified as follows:

Let vpccComponentNum be number of V-PCC components for (i = 0; i <vpccComponentNum; i++) { DpbDabOutputTime[ n ][ i ] =AuCpbCabRemovalTime[ n ][ i ] + ClockTick *  (PicAtlasDpbOutputDelay[ n][ i ] +  DpbDabDelayOffset [ n ][ i ]) + ClockSubTick * i }PicAtlasDpbOutputDelay[ n ] is the value of ith component ofpic_dpb_output_delay/atlas_dpb_output_delay in the picture/atlas timingSEI message associated with access unit n. ClockSubTick = ClockTick / (tick_divisor_minus2 + 2 )

DpbDabOutputTime[n] may be similar to AuNominalRemovalTime,AuCpbCabRemovalTime[n] may be similar toAuNominalRemovalTime[firstAtlasInCurrBuffPeriod], PicAtlasDpbOutputDelaymay be similar to AuCabRemovalDelayVal, and DpbDabDelayOffset may besimilar to CabDelayOffset. Thus, the equation above may be:

AuNominalRemovalTime[n]=AuNominalRemovalTime[firstAtlasInCurrBuffPeriod]+ClockTick*(AuCabRemovalDelayVal−CabDelayOffset),where AuNominalRemovalTime[n] is the nominal removal time of the accessunit n from the CAB when access unit n is not the first access unit of abuffering period, AuNominalRemovalTime[firstAtlasInCurrBuffPeriod] isthe nominal removal time of the first access unit of the currentbuffering period, AuCabRemovalDelayVal is the value ofAuCabRemovalDelayVal derived according to aft_cab_removal_delay_minus1in the atlas timing SEI message associated with access unit n, andCabDelayOffset is set equal to the value of the buffering period SEImessage syntax element bp_cab_delay_offset or is set equal to 0.

FIG. 13 is a schematic diagram 1300 demonstrating a maximum delaycalculation for a single map. In the schematic diagram 1300, component 0has in-order coding so that frames of component 0 are buffered in thesame order as they are displayed. Specifically, the DPB buffers frame 0,then frame 1, then frame 2, then frame 3, then frame 4, and finallyframe 5. Likewise, the display device displays frame 0, then frame 1,then frame 2, then frame 3, then frame 4, and finally frame 5. Component1 has out-of-order coding so that frames of component 1 are buffered ina different order than they are displayed. Specifically, the DPB buffersframe 0, then frame 2, then frame 1, then frame 3, then frame 5, andfinally frame 4. However, the display device can begin display only whenframe 2 is decoded, so there is a delay of 1 frame in the decodingorder. After that delay, the display device displays frame 0, then frame1, then frame 2, then frame 3, then frame 4, and finally frame 5.Component 2 also has out-of-order coding so that frames of component 2are buffered in a different order than they are displayed. Specifically,the DPB buffers frame 0, then frame 4, then frame 2, then frame 1, thenframe 3, and finally frame 5. However, the display device can begindisplay only when frame 4 is decoded, so there is a delay of 2 frames inthe decoding order. After that delay, the display device displays frame0, then frame 1, then frame 2, then frame 3, then frame 4, and finallyframe 5.

Component 2 has the biggest delay, so it dictates a maximum offset of 2frames. Component 0 has a delay of 0 frames, while the maximum offset is2 frames, so an additional offset of 2 frames is added to component 0.Component 1 has a delay of 1 frame, while the maximum offset is 2frames, so an additional offset of 1 frame is added to component 1.

When the number of maps is 1, a DAB/DPB output time delay in apicture/atlas at timing SEI of access unit n is modified as follows:

for (i = 0; i < vpccComponentNum; i++) {  if (<InterleavedMaps>) {  DpbDabOutputTime[ n ][ i ] = AuCpbCabRemovalTime[ n ][ i ] +  ClockTick * (PicAtlasDpbOutputDelay[ n ][ i ] * N −  DabOutputInterval[ n ][ i ] + DpbDabDelayOffset[ n ][ i ]) +  ClockSubTick * i  } else {   DpbDabOutputTime[ n ][ i ] =AuCpbCabRemovalTime[ n ][ i ] +   ClockTick * (PicAtlasDpbOutputDelay[ n][ i ] +   DpbDabDelayOffset[ n ][ i ]) + ClockSubTick * i  }

FIG. 14 is a schematic diagram 1400 demonstrating a maximum delaycalculation for multiple maps. The schematic diagram 1400 is similar tothe schematic diagram 1300. Specifically, component 0 has in-ordercoding, while component 1 and component 2 have out-of-order coding. Inaddition, component 2 has the biggest delay. However, unlike in theschematic diagram 1300, component 1 and component 2 in the schematicdiagram 1400 have 2 maps, map 0 and map 1. In addition, component 2dictates a maximum offset of 3 frames. Furthermore, the display devicecannot display a frame until the decoder has decoded all maps for thatframe.

When the number of maps is N, a DAB/DPB output time delay in apicture/atlas at timing SEI of access unit n is modified as follows:

for (i = 0; i < vpccComponentNum; i++) {  if (<InterleavedMaps>) {  DpbDabOutputTime[ n ][ i ] = AuCpbCabRemovalTime[ n ][ i ] +  ClockTick * (PicAtlasDpbOutputDelay[ n ][ i ] * N −  DabOutputInterval[ n ][ i ] +   DpbDabDelayOffset[ n ][ i])+ClockSubTick * i  } else {   DpbDabOutputTime[ n ][ i ] =AuCpbCabRemovalTime[ n ][ i ] +   ClockTick * (PicAtlasDpbOutputDelay[ n][ i ] +   DpbDabDelayOffset[ n ][ i ]) + ClockSubTick * i  }

DpbDabDelayOffset is derived as follows:

Set MaxInitialDelay = 0; Check for each V-PCC component, and set: for (i= 0; i < vpccComponentNum; i++) {  MaxInitialDelay = max(MaxInitDelay, PicAtlasDpbOutputDelay[n][i]) } DpbDabDelayOffset[n][i]=MaxInitialDelay − PicAtlasDpbOutputDelay[n][i])

The first instance of MaxlnitialDelay may be similar to removalDelay,the second instance of MaxlnitDelay may be similar toauCabRemovalDelayDelta, and PicAtlasDpbOutputDelay may be similar toInitCabRemovalDelay. Thus, the equation above may be:

removalDelay=Max(auCabRemovalDelayDelta,Ceil((InitCabRemovalDelay[SchedSelIdx]÷90000+offsetTime)÷ClockTick),

where removalDelay is defined as shown, auCabRemovalDelayDelta is thevalue of the syntax element (bp_atlas_cab_removal_delay_delta_minus1+1)in the buffering period SEI message associated with access unit n, andInitCabRemovalDelayOffset[SchedSelIdx] is set equal to the value of thebuffering period SEI message syntax elementbp_nal_initial_alt_cab_removal_offset[SchedSelIdx] orInitCabRemovalDelay[SchedSelIdx] is set equal to the value of thebuffering period SEI message syntax elementbp_nal_initial_cab_removal_delay[SchedSelIdx].

FIG. 15 is a flowchart illustrating a method 1500 of decoding abitstream according to a first embodiment. The decoder 400 may implementthe method 1500. The decoder 400 may be a PCC decoder. At step 1510, apoint cloud bitstream is received. At step 1520, buffering of the pointcloud bitstream, or point cloud bitstream components, is performed basedon a time. The performing comprises determining the time based on adelay and a delay offset. Finally, at step 1530, the point cloudbitstream is decoded based on the buffering.

The method 1500 may implement additional embodiments. For instance, thetime is further based on a removal time. The time is further based onClockTick. The time is further based on a first expression of the delayand the delay offset. An expression is a mathematical concept describinga meaningful combination of components. For instance, the firstexpression is (PicAtlasDpbOutputDelay[n][i]+DpbDabDelayOffset[n][i])above. In other embodiments, the first expression is a differencebetween PicAtlasDpbOutputDelay[n][i] and DpbDabDelayOffset[n][i] orbetween similar components. The time is further based on a secondexpression, and the second expression is a product of ClockTick and thefirst expression. The time is further based on a sum of the removal timeand the second expression. The point cloud bitstream comprises aplurality of components. The components comprise an occupancy map. Thecomponents comprise geometry data. The components comprise attributedata. The components comprise an atlas frame. The time is further basedon a number of the components. The time is DpbDabOutputTime. The delayis PicAtlasDpbOutputDelay. The delay offset is DpbDabDelayOffset.DpbDabDelayOffset is equal to a difference between MaxlnitialDelay andPicAtlasDpbOutputDelay.

FIG. 16 is a flowchart illustrating a method 1600 of decoding abitstream according to a second embodiment. The decoder 400 mayimplement the method 1600. The decoder 400 may be a PCC decoder. At step1610, a point cloud bitstream is received. At step 1620, buffering ofthe point cloud bitstream, or point cloud bitstream components, isperformed based on a delay. The delay is based on a first delay and asecond delay. Finally, at step 1630, the point cloud bitstream isdecoded based on the buffering.

The method 1600 may implement additional embodiments. For instance, thedelay is further based on a maximum of the first delay and the seconddelay. The delay is MaxlnitialDelay. The first delay is MaxlnitDelay.The second delay is PicAtlasDpbOutputDelay. The buffering is furtherbased on DpbDabDelayOffset, and whereinDpbDabDelayOffset=MaxlnitialDelay−PicAtlasDpbOutputDelay.

In an embodiment, a receiving means receives a point cloud bitstream. Aprocessing means performs buffering of the point cloud bitstream basedon a time. The performing comprises determining the time based on adelay and a delay offset. The processing means decodes the point cloudbitstream based on the buffering.

The term “about” means a range including ±10% of the subsequent numberunless otherwise stated. While several embodiments have been provided inthe present disclosure, it may be understood that the disclosed systemsand methods might be embodied in many other specific forms withoutdeparting from the spirit or scope of the present disclosure. Thepresent examples are to be considered as illustrative and notrestrictive, and the intention is not to be limited to the details givenherein. For example, the various elements or components may be combinedor integrated in another system or certain features may be omitted, ornot implemented.

In addition, techniques, systems, subsystems, and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, components, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled may be directly coupled or maybe indirectly coupled or communicating through some interface, device,or intermediate component whether electrically, mechanically, orotherwise. Other examples of changes, substitutions, and alterations areascertainable by one skilled in the art and may be made withoutdeparting from the spirit and scope disclosed herein.

What is claimed is:
 1. A method implemented by a point cloud compression(PCC) decoder and comprising: receiving, by the PCC decoder, a pointcloud bitstream comprising components; performing, by the PCC decoder,buffering of the point cloud bitstream based on a time, wherein the timeis based on a delay and a delay offset; and decoding, by the PCCdecoder, the point cloud bitstream based on the buffering.
 2. The methodof claim 1, wherein the time is further based on a removal time.
 3. Themethod of claim 2, wherein the time is further based on ClockTick. 4.The method of claim 3, wherein the time is further based on a firstexpression of the delay and the delay offset.
 5. The method of claim 4,wherein the time is further based on a second expression, and whereinthe second expression is a product of ClockTick and the firstexpression.
 6. The method of claim 5, wherein the time is further basedon a sum of the removal time and the second expression.
 7. The method ofclaim 1, wherein the point cloud bitstream comprises a plurality ofcomponents.
 8. The method of claim 7, wherein the components comprise anoccupancy map, geometry data, attribute data, or an atlas frame.
 9. Themethod of claim 7, wherein the time is further based on a number of thecomponents.
 10. The method of claim 1, wherein the time isDpbDabOutputTime.
 11. The method of claim 1, wherein the delay isPicAtlasDpbOutputDelay.
 12. The method of claim 1, wherein the delayoffset is DpbDabDelayOffset.
 13. The method of claim 1, whereinDpbDabDelayOffset is equal to a difference between MaxlnitialDelay andPicAtlasDpbOutputDelay.
 14. The method of claim 1, further comprising:storing the point cloud bitstream; and displaying a picture or a videofrom the point cloud bitstream.
 15. A point cloud compression (PCC)decoder comprising: a memory configured to store instructions; and aprocessor coupled to the memory and configured to execute theinstructions to cause the PCC decoder to: receive a point cloudbitstream comprising components; perform buffering of the point cloudbitstream based on a time, wherein the time is based on a delay and adelay offset; and decode the point cloud bitstream based on thebuffering.
 16. A method implemented by a point cloud compression (PCC)decoder and comprising: receiving, by the PCC decoder, a point cloudbitstream; performing, by the PCC decoder, buffering of the point cloudbitstream based on a delay, wherein the delay is based on a first delayand a second delay; and decoding, by the PCC decoder, the point cloudbitstream based on the buffering.
 17. The method of claim 16, whereinthe delay is further based on a maximum of the first delay and thesecond delay.
 18. The method of claim 17, wherein the delay isMaxlnitialDelay, wherein the first delay is MaxlnitDelay, and whereinthe second delay is PicAtlasDpbOutputDelay.
 19. The method of claim 18,wherein the buffering is further based on DpbDabDelayOffset, and whereinDpbDabDelayOffset=MaxlnitialDelay−PicAtlasDpbOutputDelay.
 20. The methodof claim 16, further comprising: storing the point cloud bitstream; anddisplaying a picture or a video from the point cloud bitstream.